Tsuneaki Hiramatsu knew something was up. It was the end of December and his amateur photo blog had suddenly jumped from a handful of visitors a day to thousands. The telephone customer service agent and hobby photographer was surprised.

“I was like, what happened?!” says the 35-year-old Hiramatsu, who lives in Okayama City, Japan.

What happened was that Hiramatsu’s long exposure and time-lapse photos of Japanese fireflies had started to go viral. Someone, somewhere, had re-posted his photos and they were spreading across the blogosphere like wildfire.

On Dec. 18, the photos appeared on a Tumblr blog called Polaroid Dreams. More than 24,000 people have subsequently liked and reblogged that post.

Christopher Jobson, whose art and design blog Colossal got four million hits last month, was one of those who reposted the photos from Polaroid Dreams, furthering the viral spread.

“I’d never seen anything like it before,” Jobson says. “The photos look digital, or like the image was manufactured. But then you realize that it’s just time-lapse photography that has been wonderfully executed.” (This is not entirely true, as some of the photos are composites of multiple images.)

From there the photos continued to jump around the internet, popping up on countless other blogs as well as sites like My Modern Met and the website of the French newspaper Le Figaro.

Hiramatsu is not sure how far the photos have traveled, but the spread continues. He was thrilled when the American Museum of Natural History recently contacted him about using his photos to help promote an upcoming exhibition called “Creatures of Light: Nature’s Bioluminescence.”

“I’ve just been really surprised,” says Hiramatsu, who remains very humble about his recent success and is not planning on leaving his day job at the Nippon Telegraph and Telephone Corporation, or NTT.

Clearly, though, the photos have resonated with a wide audience.

Hiramatsu took them at various points over a three-year period between 2008 and 2011 and they are from two different sites in the Okayama prefecture.

The long-exposure photos near the river were taken near Okayama City in the Hokubo area, and capture a certain type of firefly called the Genji Botaru. The photos in the woods were taken near Niimi City and the famous Tennoohachiman shrine and capture the Hime Botaru.

To make the photo where you see hundreds, if not thousands, of small firefly lights, Hiratmatsu used time-lapse photography to take several continuous exposures and then combined those exposures in post-production. Each photo where the firefly lights become trails is just one long exposure.

Hiratmatsu says he’s not the first to use these techniques to shoot Japanese fireflies. He openly admits borrowing them from other photographers who have posted tutorials on their own websites.

Nonetheless, it was Hiramatsu’s photos that took off. And while we might never know patient zero in his viral success, the spread is testament to their effect on viewers. He’s currently looking forward to upgrading to the Nikon D800 and continuing to learn more about photography — in part by shooting more fireflies.

An earlier reference about how to say firefly in Japanese was deleted due to a grammatical error.